<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            height: 15px;
            width: 200px;
            border: 1px solid #000000;
            position: relative;
        }
        div::after {
            content: '';
            width: 3px;
            height: 3px;
            position: absolute;
            right: 5px;
            top: 5px;
            border-right: 1px solid #000000;
            border-bottom: 1px solid #000000;
            transform: rotate(-45deg);
            transition: all 0.3s;
        }
        div:hover::after {
            transform: rotate(45deg);
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>